1. Field of the Invention
The present invention relates to an apparatus for detecting shake such as camera shake given, for example, to an electronic camera, and an apparatus for correcting a photographing optical system against the shake based on a shake detection result.
2. Description of the Background Art
There have been widely known image pickup apparatuses having a so-called camera-shake correcting function in order to enable secure photographing in cases where “shake” such as camera shake is likely to occur during the photographing by a telephoto lens or of an object in the dark (requiring a longer exposure) with the apparatuses hand-held. This camera-shake correcting function corrects a displacement of an optical axis by driving a shake-correcting optical system or an image pickup device based on shake in the case of the displacement of the optical axis resulting from the shake given to the image pickup apparatus, for example, due to the hand shake of a user.
In the image pickup apparatus having the camera-shake correcting function is provided a shake detecting sensor including, for example, a gyroscope for detecting a shake amount of the image pickup apparatus. A shake correction control unit calculates a shake angle of the image pickup apparatus by integrating outputs of the shake detecting sensor, and drives the shake-correcting optical system based on the shake angle information.
A detection output of the shake detecting sensor when the image pickup apparatus is stationary has a relatively large individual difference, and changes according to an environmental temperature. Thus, the shake detecting sensor is normally connected with an amplifier via a high-pass filter constructed by a capacitor and a resistance element so as to remove direct-current components from an output signal of the shake detecting sensor.
Japanese Unexamined Patent Publication No. H08-82823 discloses a camera having a shake correcting function of calculating a shake amount of the camera from an output signal of an angular velocity sensor and correcting a movement of an object image on a light receiving surface by driving a correcting optical system arranged on a light path of a photographing optical system based on the calculated shake amount. In this publication, direct-current cutting means for cutting direct-current components contained in an output voltage of the angular velocity sensor is comprised of subtracting means for subtracting a direct-current component voltage V3 from an output voltage V1 of the angular velocity sensor, direct-current detecting means for calculating the direct-current components based on an output voltage V2 of the subtracting means by an operation of (V3+V2/Kx), and setting means for setting a detection criterion of the direct-current detecting means by changing the coefficient Kx. This direct-current cutting means cuts up to relatively high frequency components by setting the coefficient Kx at a relatively small value K1 during a period until a light measurement switch is turned on after the camera is powered, continuously changes the coefficient Kx from the value K1 to a value K2 larger than K1 during a period until a specified time lapses after the light measurement switch is turned on, and cuts only relatively low frequency components by setting the coefficient Kx at the value K2 thereafter.
In the case of providing the high-pass filter constructed by the capacitor and the resistance element, an output signal of the shake detecting sensor comes to contain relatively more direct-current components, for example, when the image pickup apparatus is panned. As a result, the high-pass filter outputs a signal containing direct-current components with an opposite sign (however, attenuated by a time constant of the high-pass filter), whereby a wrong detection result (detection angle) is generated to lead to a reduction in shake correcting performance.